The latest-generation BMW M4 has yet to be unveiled but already, a prototype of what appears to be a new variant has been spied testing.

The camouflaged car was recently spied testing in Europe and looks to be a more performance-focused version of the M4, prompting speculation it could be dubbed the GTS. Whatever it is called, it is clear that it has been heavily modified over the regular M4.

The first thing that will catch your eye is the odd exhaust layout. Perhaps taking inspiration from the controversial ‘stacked’ tailpipes of the Lexus IS F and Ferrari California, BMW’s designers have fitted similar tailpipes but placed them in the center of the rear fascia. It is a strange design choice but BMW has been making other controversial design decisions recently, most notably with the huge kidney grilles of the new M3 and M4.

Beyond the exhaust layout, this BMW M4 prototype features a fixed rear wig as well as a custom rear diffuser. The rear bumper also appears to sport subtle fins on either side to help with aerodynamics. The front wheel arches also appear a touch wider.

If this is indeed a prototype for a BMW M4 GTS, it will inevitably benefit from a series of performance modifications. This will likely include upgrades to the 3.0-liter twin-turbocharged six-cylinder engine to give it some added horsepower and torque. BMW can also be expected to shed some pounds from the car while also fitting new suspension and braking components.